Fluid sealing device



June 12, 1951 STEWART 2,557,039

FLUID SEALING DEVICE Filed Oct. 20, 1945 FI E" INVENIOR. JOHN H. F. STEWART ATTORNEY Patented June 12,1951

UNITED STATES ATENT OFFICE FLUID SEALING DEVICE John H. F. Stewart, Detroit, Mich.

Application October 20, 1945, Serial No. 623,501-

This invention relates to sealing devices such as are used to forma-fluid-tight seal with acylindrical surface commonly known as oil seals and used, for example, on sliding pistons, piston rods, rotating shafts and the like. In thepatent to Stewart, No. 2,332,763, there is disclosed a fluid sealing device 'in which a tubular sealing sleeve of flexible material is confined between two guide surfaces of generally toroidal form so that the sealing sleeve is projected, first, axially and then along the toroidal surface radially into engagement with the cylindrical surface to besealed.

It is an object of the present invention to inrprove the construction of the seal disclosed in the Stewart patent for certain specialized applications and to provide a seal construction having improved efiiciency, longer life and lower cost.

In the seal disclosed in the aforesaid patent the sealing sleeve is closely confined between two curved guide surfaces along its entire length. a I has been found that, while this construction is eminently suitable for a great manyapplications. there are other specialized cases in which seals of this construction are not adequate. Thus, in a seal used on a piston sliding in a long, relatively thin-walled cylinder operating at very high pressures, it has been found that the friction of the sealing sleeve on both guide surfaces sometimes interferes with the necessary in-and-out action of the sealing sleeve which is required due to the stretch of the cylinder walls under high pressure. This stretch does not occur uniformly throughout the length of the cylinder due to the additional strength provided by the cylinder headv Consequently, it is necessary in one piston stroke for the seal to move in and out for a substantial distance in order to maintain contact with the cylinder walls, and this action is sometimes pre-' vented by the friction of the sealing sleeve in "contact with the guide surfaces of the housing.

According to the present invention, it has been found that a sealing sleeve, which is unsupported by the guide surfaces of the housing except along the outer toroidal surface where the sealing sleev is deflected from an axial direction to a radial direction, and thus becomes floated in a body of fluid, will greatly facilitate projection and retraction of the sealing lip.

It is also an object of the present invention therefore, to provide a sealing device wherein a tubular sleeve is guided along a toroidal surface by endwise pressure into contact with a cylindrical surface to be sealed and in which the tubular portion of the sleeve is supported upon. the fluid being sealed, at least throughout a portion of its length.

Another object is to provide a seal of this char acter in which inexpensive stamped parts of sheet metal may be utilized in place of parts turned from solid stock.

3 Claims. ('01. 309-26) Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing wherein a preferred form of the present invention is clearly shown.

In the drawing:

Figure 1 is across-sectional view of an oil seal particularly adapted for sliding pistons incorporating a preferred form of the present invention.

Figure 2 is a cross-sectional view of an oil seal particularly adapted for sliding or rotating shafts and incorporating another form of the present invention. V

Figure 3 is a cross-sectional view of an oil seal particularly adapted for sliding or rotating shafts and incorporating another form of the present invention.

In the construction illustrated in Figure 1, a piston til is provided with a counterbore G2 in which an oil seal assembly is is retained by a re tainer plate H5. in a groove 26 seals the counterbore i2 against leakage. I

The seal It comprises a main housing 22 having a toroidal guide surface 24 with a straight cylindrical portion 26 and terminating at 28 substantially perpendicular to the cylinder wall 3 2?. An abutment member 32 has a flange 3d which is staked to the main housing 22 and is provided with a generally complementary toroidal surface 35 spaced from the guide surface 24. Between the surfaces 24 and 36 there is mounted a flexible sealing ring 33. The ring 38 is thinner than the space between the surfaces 24 and 36 and has tubular extension ill which is spaced from the ey lindrical portion 26 of the guide surface as weli as from the abutment 32. The ring 38 may provided with a pointed nose at 52 adapted to be wedged between the cylinder wall iii and the outer corner of the abutment 32. A suitable follower washer 4 and spring 46 serve to project the sealing ring 38 axially into contact with the toroidal portion of guide surface 24 and radially outward into contact with the cylinder wall 36. A series of holes G8 are provided in the flange for the admission of pressure fluid which also projects the sealing ring endwise in addition to the spring.

In operation, with the parts assembled in the position illustrated, and when there is no' fluid pressure imposed on the left face of the piston E8, the spring 58 abuts against the left-hand end of the sealing ring 38 with a predetermined pressure which is transmitted endwise through the ring and, due to the curvature of the surface 24, maintains the ring in contact with the wall 30 at the nose 42. This wedges the latter against the corner of the abutment .32 and effectively A suitable oil seal 58 mounted 1 prevents leakage of oil rightwardly along the clearance space 50.

Upon the application of fluid pressure to the left face of piston [0, this pressure is admitted through the holes 48 and acts upon the face of the follower M and upon both the inner and outer side surfaces of the cylindrical portion 46 of sealing ring 38. These latter actions are in a radial direction and, being equal and opposite, produce no net force on the ring 38. The endwise pressure, however, is transmitted from the follower 44 to the end face of the ring 38 and tends to thrust it to the right where it is deflected by the toroidal surface 24 to project the ring 38 radially outward into tighter contact with the cylinder wall 3B. When very high pressures are applied, the wall at will expand signiflcantly, and the sealing ring 38 will be projected outwardly to follow any movement of the wall 35. As the piston H3 travels the length of the cylinder, the amount of expansion of wall 30 under fluid pressure will vary at different distances from the head end of the cylinder.

Due to the floating of a substantial portion of the length of sealing ring 38 upon a body of fluid and out of contact with the guide surface 24 and abutment 32, the sealing ring 38 has ample freedom of action to move inwardly and outwardly following the contours of the cylinder wall 39.

In Figure 2 there is illustrated a modified form of the present invention particularly adapted for sealing a sliding or rotating shaft. In the construction illustrated, a counterbore I2 is formed in a stationary housing part it to receive an oil seal assembly hi held in place by a retainer plate The main housing member 22 and other parts identified by the same reference numerals may be identical to those previously described. The abutment 3'2, however, for lower cost of manufacture is made from a stamped or drawn sheet metal piece of generally tubular form having a flange M which is staked to the main housing 22. The righthand end of the abutment 32' is provided with a rounded nose at 36 to act as an abutment to prevent leftward movement of the sealing lip 52 of the sealing ring 38 when sealing against high pressures.

The sealing ring 33 differs from the previously-described sealing ring in that the cylindrical portion i=3 may contact the cylindricai portion 26 of the guide surface 24. The foilower abutment 54 may also be of beveled form as is the end surface of sealing ring 38' to wedge the end of the sealing ring outwardly into contact with the surface 2%.

The action of the seal is similar to that previously described except that in the present case, where the member to be sealed, such as the shaft 35', does not partake of any substantial radial motion, the friction of the sealing ring along the guide surface of the housing does not interfere with proper sealing action. In addition, contact of the portion d9 of the sealing ring with surface 26 is desirable under conditions where at times the pressure difference across the seal may be reversed; that is, the side which is normally subjected to pressure may at times be subjected to a vacuum. Under these conditions, the beveled follower 54 wedges the back end of the sealing ring into engagement with the surface 26 tightly and prevents entrance of air to the mechanism which otherwise might leak along the surfaces 28, 24 and 26.

In the form of the invention illustrated in Figure 3, there is shown a seal for light-duty service of inexpensive construction wherein the sealing ring is entirely unsupported on its inner side and there is no abutment other than the shaft 38' for the sealing lip of the seal. This seal differs from the construction shown in Figure 2 in that the abutment member comprises merely a flat washer 32 staked to the housing 22 and providing a clearance 50 with the shaft 39 through which fluid pressure is applied to the entire inner contour of the sealing ring 38". The latter may have a flat end for the follower 4i and not be adapted for sealing against a vacuum.

The action of this seal will be readily understood from the previous description, it being apparent that this construction is well suited for light-duty applications wherein high pressures or vacuums are not applied to the seal.

While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. In a device for forming a fluid seal with a cylindrical surface, the combination of a housing member having a guide surface spaced from the cylindrical surface and including a toroidal portion terminating adjacent and substantially perpendicular to the sealing surface, a flexible sealing ring having a complemental toroidal surface in contact with said toroidal portion and having a cylindrical extension beyond the toroidal surface and spaced from the cylindrical surface, means for forcing the sealing ring axially toward the toroidal portion of the guide surface, said cylindrical extension being free from mechanical support radially along at least the full length of the concave toroidal surface and extension and subject in a radial direction to only fluid pressure forces, and means forming an abutment for the end of the sealing ring adjacent the cylindrical surface and on the opposite side thereof from the toroidal guide surface.

2. In a device for forming a fluid seal with a cylindrical surface, the combination of a housing member having a guide surface spaced from the cylindrical surface and including a toroidal portion terminating adjacent and substantially perpendicular to the sealing surface, a flexible sealing ring having a complemental toroidal surface in contact with said toroidal portion and having a cylindrical extension beyond the toroidal surface and spaced from the cylindrical surface, means for forcing the sealing ring axially toward the toroidal portion of the guide surface, said cylindrical extension being free from mechanical support radially along at least the full length of the concave toroidal surface and extension and subject in a radial direction to only fluid pressure forces, and a sheet metal member comprising a tubular portion adjacent the cylindrical surface and a perpendicular flange portion secured to the housing for providing an abutment for the end of the sealing ring adjacent the cylindrical surface and on the opposite side thereof from the toroidal guide surface.

3. In a device for forming a fluid seal with a cylindrical surface, the combination of a housing member having a guide surface spaced from the cylindrical surface and including a toroidal portion terminating adjacent and substantially per- S pendicular to the sealing surface, a flexible sealing ring having a complemental toroidal surface in contact with said toroidal portion and having a cylindrical extension beyond the toroidal surface and spaced from the cylindrical surface, means for forcing the sealing ring axially toward the toroidal portion of the guide surface, said cylindrical extension being free from mechanical support radially along at least the full length of the concave toroidal surface and extension and subject in a radial direction to only fluid pressure forces, and a complemental abutment member associated with the housing having a surface generally parallel to and spaced from the guide surface providing an abutment for the end of the sealing ring adjacent the cylindrical surface and on the opposite side thereof from the toroidal guide surface of the housing, said abutment mem- .6 her being spaced from the cylindrical extension of the sealing ring.

JOHN H. F. STEWART.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,682,222 Greenidge Aug. 28, 1928 2,332,763 Stewart Oct. 26, 1943 2,401,379 Smith June 4, 1946 2,404,664 Skinner July 23, 1946 FOREIGN PATENTS Number Country Date 168,517 Switzerland of 1934 

